Understanding the viscous behavior of silica-based molten fluxes is essential in maintaining the reliability of steel casting operations and in preventing breakouts. In particular, high concentrations of aluminum in recently developed transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) steels tend to promote reduction of silica in the mold fluxes that result in the formation of alumina, which in turn increases the viscosity. To counteract this effect, significant amounts of fluidizers such as CaF 2 and Li 2 O are required to ensure that mold fluxes have acceptable lubrication and heat transfer characteristics. The viscous behavior of the slag system based on CaO-SiO 2 -12 wt pct Na 2 O with various concentrations of CaF 2 and Li 2 O has been studied using the rotating spindle method to understand the effects on the viscosity with these additives. CaF 2 additions up to 8 wt pct were effective in decreasing the viscosity by breaking the network structure of molten fluxes, but CaF 2 concentrations above this level had a negligible effect on viscosity. Li 2 O additions up to 2 wt pct were also effective in decreasing the viscosity, but the effect was comparatively negligible above 2 wt pct. Using Fourier transform infrared (FTIR) analysis of as-quenched slag samples, it was concluded that the viscosity was controlled more effectively by changing the larger complex silicate structures of rings and chains than by changing the amounts of simpler dimers and monomers.

HYUN-SHIK PARK, SU SANG PARK, and IL SOHNUnderstanding the viscous behavior of copper smelting slags is essential in increasing the process efficiency and obtaining the discrete separation between the matte and the slag. The viscosity of the FeO t -SiO 2 -Al 2 O 3 copper smelting slags was measured in the current study using the rotating spindle method. The viscosity at a fixed Al 2 O 3 concentration decreased with increasing Fe/SiO 2 ratio because of the depolymerization of the molten slag by the networkmodifying free oxygen ions (O 2À ) supplied by FeO. The Fourier transform infrared (FTIR) analyses of the slag samples with increasing Fe/SiO 2 ratio revealed that the amount of large silicate sheets decreased, whereas the amount of simpler silicate structures increased. Al 2 O 3 additions to the ternary FeO t -SiO 2 -Al 2 O 3 slag system at a fixed Fe/SiO 2 ratio showed a characteristic V-shaped pattern, where initial additions decreased the viscosity, reached a minimum, and increased subsequently with higher Al 2 O 3 content. The effect of Al 2 O 3 was considered to be related to the amphoteric behavior of Al 2 O 3 , where Al 2 O 3 initially behaves as a basic oxide and changes to an acidic oxide with variation in slag composition. Furthermore, Al 2 O 3 additions also resulted in the high temperature phase change between fayalite/hercynite and the modification of the liquidus temperature with Al 2 O 3 additions affecting the viscosity of the copper smelting slag.

Shape memory polyurethane (SMPU) flexibly crosslinked by a hydrophobic poly(dimethylsiloxane) (PDMS) spacer at its side through allophanate bonding was tested for shape recovery at À30 C and compared to a linear SMPU. The SMPU was composed of 4,4 0 -methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD), and PDMS that was connected to SMPU chains by a second MDI. The mechanical and shape memory properties of two types of SMPU, differing in PTMG and PDMS content, were compared. In the best case, a 283% increase in maximum stress compared to the linear polymer was attained without any sacrifice of strain. Shape recovery at 45 C increased to 91% and remained at more than 80% after four cyclic tests. Shape recovery at 0 C could be improved by increasing PDMS content, and the critical shape recovery temperature decreased with increasing PDMS content. The PDMScrosslinked SMPU demonstrated instant shape recovery at À30 C in comparison with the linear SMPU that must be warmed to room temperature for complete shape recovery. The extraordinary shape memory results were analyzed and are discussed together with differential scanning calorimetry and infrared data.